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1307 lines
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<html>
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
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<meta encoding="utf8">
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<link rel="stylesheet" href="llvm.css" type="text/css">
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<title>LLVM 2.8 Release Notes</title>
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</head>
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<body>
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<div class="doc_title">LLVM 2.8 Release Notes</div>
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<img align=right src="http://llvm.org/img/DragonSmall.png"
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width="136" height="136" alt="LLVM Dragon Logo">
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<ol>
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<li><a href="#intro">Introduction</a></li>
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<li><a href="#subproj">Sub-project Status Update</a></li>
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<li><a href="#externalproj">External Projects Using LLVM 2.8</a></li>
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<li><a href="#whatsnew">What's New in LLVM 2.8?</a></li>
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<li><a href="GettingStarted.html">Installation Instructions</a></li>
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<li><a href="#knownproblems">Known Problems</a></li>
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<li><a href="#additionalinfo">Additional Information</a></li>
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</ol>
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<div class="doc_author">
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<p>Written by the <a href="http://llvm.org">LLVM Team</a></p>
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</div>
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<!--
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<h1 style="color:red">These are in-progress notes for the upcoming LLVM 2.8
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release.<br>
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You may prefer the
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<a href="http://llvm.org/releases/2.7/docs/ReleaseNotes.html">LLVM 2.7
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Release Notes</a>.</h1>
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-->
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<!-- *********************************************************************** -->
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<div class="doc_section">
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<a name="intro">Introduction</a>
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</div>
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<!-- *********************************************************************** -->
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<div class="doc_text">
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<p>This document contains the release notes for the LLVM Compiler
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Infrastructure, release 2.8. Here we describe the status of LLVM, including
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major improvements from the previous release and significant known problems.
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All LLVM releases may be downloaded from the <a
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href="http://llvm.org/releases/">LLVM releases web site</a>.</p>
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<p>For more information about LLVM, including information about the latest
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release, please check out the <a href="http://llvm.org/">main LLVM
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web site</a>. If you have questions or comments, the <a
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href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVM Developer's
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Mailing List</a> is a good place to send them.</p>
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<p>Note that if you are reading this file from a Subversion checkout or the
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main LLVM web page, this document applies to the <i>next</i> release, not the
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current one. To see the release notes for a specific release, please see the
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<a href="http://llvm.org/releases/">releases page</a>.</p>
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</div>
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<!--
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Almost dead code.
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include/llvm/Analysis/LiveValues.h => Dan
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lib/Transforms/IPO/MergeFunctions.cpp => consider for 2.8.
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GEPSplitterPass
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-->
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<!-- Features that need text if they're finished for 2.9:
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combiner-aa?
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strong phi elim
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loop dependence analysis
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TBAA
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CorrelatedValuePropagation
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-->
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<!-- Announcement, lldb, libc++ -->
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<!-- *********************************************************************** -->
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<div class="doc_section">
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<a name="subproj">Sub-project Status Update</a>
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</div>
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<!-- *********************************************************************** -->
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<div class="doc_text">
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<p>
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The LLVM 2.8 distribution currently consists of code from the core LLVM
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repository (which roughly includes the LLVM optimizers, code generators
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and supporting tools), the Clang repository and the llvm-gcc repository. In
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addition to this code, the LLVM Project includes other sub-projects that are in
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development. Here we include updates on these subprojects.
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</p>
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</div>
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<!--=========================================================================-->
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<div class="doc_subsection">
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<a name="clang">Clang: C/C++/Objective-C Frontend Toolkit</a>
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</div>
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<div class="doc_text">
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<p><a href="http://clang.llvm.org/">Clang</a> is an LLVM front end for the C,
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C++, and Objective-C languages. Clang aims to provide a better user experience
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through expressive diagnostics, a high level of conformance to language
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standards, fast compilation, and low memory use. Like LLVM, Clang provides a
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modular, library-based architecture that makes it suitable for creating or
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integrating with other development tools. Clang is considered a
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production-quality compiler for C, Objective-C, C++ and Objective-C++ on x86
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(32- and 64-bit), and for darwin-arm targets.</p>
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<p>In the LLVM 2.8 time-frame, the Clang team has made many improvements:</p>
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<ul>
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<li>Clang C++ is now feature-complete with respect to the ISO C++ 1998 and 2003 standards.</li>
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<li>Added support for Objective-C++.</li>
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<li>Clang now uses LLVM-MC to directly generate object code and to parse inline assembly (on Darwin).</li>
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<li>Introduced many new warnings, including <code>-Wmissing-field-initializers</code>, <code>-Wshadow</code>, <code>-Wno-protocol</code>, <code>-Wtautological-compare</code>, <code>-Wstrict-selector-match</code>, <code>-Wcast-align</code>, <code>-Wunused</code> improvements, and greatly improved format-string checking.</li>
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<li>Introduced the "libclang" library, a C interface to Clang intended to support IDE clients.</li>
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<li>Added support for <code>#pragma GCC visibility</code>, <code>#pragma align</code>, and others.</li>
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<li>Added support for SSE, AVX, ARM NEON, and AltiVec.</li>
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<li>Improved support for many Microsoft extensions.</li>
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<li>Implemented support for blocks in C++.</li>
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<li>Implemented precompiled headers for C++.</li>
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<li>Improved abstract syntax trees to retain more accurate source information.</li>
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<li>Added driver support for handling LLVM IR and bitcode files directly.</li>
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<li>Major improvements to compiler correctness for exception handling.</li>
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<li>Improved generated code quality in some areas:
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<ul>
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<li>Good code generation for X86-32 and X86-64 ABI handling.</li>
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<li>Improved code generation for bit-fields, although important work remains.</li>
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</ul>
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</li>
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</ul>
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</div>
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<!--=========================================================================-->
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<div class="doc_subsection">
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<a name="clangsa">Clang Static Analyzer</a>
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</div>
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<div class="doc_text">
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<p>The <a href="http://clang-analyzer.llvm.org/">Clang Static Analyzer</a>
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project is an effort to use static source code analysis techniques to
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automatically find bugs in C and Objective-C programs (and hopefully <a
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href="http://clang-analyzer.llvm.org/dev_cxx.html">C++ in the
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future</a>!). The tool is very good at finding bugs that occur on specific
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paths through code, such as on error conditions.</p>
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<p>The LLVM 2.8 release fixes a number of bugs and slightly improves precision
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over 2.7, but there are no major new features in the release.
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</p>
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</div>
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|
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<!--=========================================================================-->
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<div class="doc_subsection">
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<a name="dragonegg">DragonEgg: llvm-gcc ported to gcc-4.5</a>
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</div>
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<div class="doc_text">
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<p>
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<a href="http://dragonegg.llvm.org/">DragonEgg</a> is a port of llvm-gcc to
|
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gcc-4.5. Unlike llvm-gcc, dragonegg in theory does not require any gcc-4.5
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modifications whatsoever (currently one small patch is needed) thanks to the
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new <a href="http://gcc.gnu.org/wiki/plugins">gcc plugin architecture</a>.
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DragonEgg is a gcc plugin that makes gcc-4.5 use the LLVM optimizers and code
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generators instead of gcc's, just like with llvm-gcc.
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</p>
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<p>
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DragonEgg is still a work in progress, but it is able to compile a lot of code,
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for example all of gcc, LLVM and clang. Currently Ada, C, C++ and Fortran work
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well, while all other languages either don't work at all or only work poorly.
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For the moment only the x86-32 and x86-64 targets are supported, and only on
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linux and darwin (darwin may need additional gcc patches).
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</p>
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<p>
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The 2.8 release has the following notable changes:
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<ul>
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<li>The plugin loads faster due to exporting fewer symbols.</li>
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<li>Additional vector operations such as addps256 are now supported.</li>
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<li>Ada global variables with no initial value are no longer zero initialized,
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resulting in better optimization.</li>
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<li>The '-fplugin-arg-dragonegg-enable-gcc-optzns' flag now runs all gcc
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optimizers, rather than just a handful.</li>
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<li>Fortran programs using common variables now link correctly.</li>
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<li>GNU OMP constructs no longer crash the compiler.</li>
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</ul>
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</div>
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<!--=========================================================================-->
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<div class="doc_subsection">
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<a name="vmkit">VMKit: JVM/CLI Virtual Machine Implementation</a>
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</div>
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<div class="doc_text">
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<p>
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The <a href="http://vmkit.llvm.org/">VMKit project</a> is an implementation of
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a Java Virtual Machine (Java VM or JVM) that uses LLVM for static and
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just-in-time compilation. As of LLVM 2.8, VMKit now supports copying garbage
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collectors, and can be configured to use MMTk's copy mark-sweep garbage
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collector. In LLVM 2.8, the VMKit .NET VM is no longer being maintained.
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|
</p>
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</div>
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|
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<!--=========================================================================-->
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<div class="doc_subsection">
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<a name="compiler-rt">compiler-rt: Compiler Runtime Library</a>
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</div>
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<div class="doc_text">
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<p>
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The new LLVM <a href="http://compiler-rt.llvm.org/">compiler-rt project</a>
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|
is a simple library that provides an implementation of the low-level
|
|
target-specific hooks required by code generation and other runtime components.
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|
For example, when compiling for a 32-bit target, converting a double to a 64-bit
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|
unsigned integer is compiled into a runtime call to the "__fixunsdfdi"
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function. The compiler-rt library provides highly optimized implementations of
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this and other low-level routines (some are 3x faster than the equivalent
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libgcc routines).</p>
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<p>
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All of the code in the compiler-rt project is available under the standard LLVM
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License, a "BSD-style" license. New in LLVM 2.8, compiler_rt now supports
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soft floating point (for targets that don't have a real floating point unit),
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and includes an extensive testsuite for the "blocks" language feature and the
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blocks runtime included in compiler_rt.</p>
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</div>
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<!--=========================================================================-->
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<div class="doc_subsection">
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<a name="lldb">LLDB: Low Level Debugger</a>
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</div>
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<div class="doc_text">
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<p>
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<a href="http://lldb.llvm.org/">LLDB</a> is a brand new member of the LLVM
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umbrella of projects. LLDB is a next generation, high-performance debugger. It
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|
is built as a set of reusable components which highly leverage existing
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libraries in the larger LLVM Project, such as the Clang expression parser, the
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LLVM disassembler and the LLVM JIT.</p>
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|
<p>
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LLDB is in early development and not included as part of the LLVM 2.8 release,
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|
but is mature enough to support basic debugging scenarios on Mac OS X in C,
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Objective-C and C++. We'd really like help extending and expanding LLDB to
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|
support new platforms, new languages, new architectures, and new features.
|
|
</p>
|
|
|
|
</div>
|
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<!--=========================================================================-->
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<div class="doc_subsection">
|
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<a name="libc++">libc++: C++ Standard Library</a>
|
|
</div>
|
|
|
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<div class="doc_text">
|
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<p>
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<a href="http://libcxx.llvm.org/">libc++</a> is another new member of the LLVM
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family. It is an implementation of the C++ standard library, written from the
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|
ground up to specifically target the forthcoming C++'0X standard and focus on
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delivering great performance.</p>
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<p>
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As of the LLVM 2.8 release, libc++ is virtually feature complete, but would
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benefit from more testing and better integration with Clang++. It is also
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|
looking forward to the C++ committee finalizing the C++'0x standard.
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|
</p>
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|
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</div>
|
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|
|
|
|
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<!--=========================================================================-->
|
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<div class="doc_subsection">
|
|
<a name="klee">KLEE: A Symbolic Execution Virtual Machine</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
<p>
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|
<a href="http://klee.llvm.org/">KLEE</a> is a symbolic execution framework for
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|
programs in LLVM bitcode form. KLEE tries to symbolically evaluate "all" paths
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through the application and records state transitions that lead to fault
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|
states. This allows it to construct testcases that lead to faults and can even
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be used to verify some algorithms.
|
|
</p>
|
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<p>Although KLEE does not have any major new features as of 2.8, we have made
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various minor improvements, particular to ease development:</p>
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<ul>
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<li>Added support for LLVM 2.8. KLEE currently maintains compatibility with
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LLVM 2.6, 2.7, and 2.8.</li>
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<li>Added a buildbot for 2.6, 2.7, and trunk. A 2.8 buildbot will be coming
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soon following release.</li>
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<li>Fixed many C++ code issues to allow building with Clang++. Mostly
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complete, except for the version of MiniSAT which is inside the KLEE STP
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version.</li>
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<li>Improved support for building with separate source and build
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directories.</li>
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<li>Added support for "long double" on x86.</li>
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<li>Initial work on KLEE support for using 'lit' test runner instead of
|
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DejaGNU.</li>
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<li>Added <tt>configure</tt> support for using an external version of
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STP.</li>
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</ul>
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</div>
|
|
|
|
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<!-- *********************************************************************** -->
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<div class="doc_section">
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<a name="externalproj">External Open Source Projects Using LLVM 2.8</a>
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</div>
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|
<!-- *********************************************************************** -->
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<div class="doc_text">
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<p>An exciting aspect of LLVM is that it is used as an enabling technology for
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a lot of other language and tools projects. This section lists some of the
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projects that have already been updated to work with LLVM 2.8.</p>
|
|
</div>
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|
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<!--=========================================================================-->
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<div class="doc_subsection">
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<a name="tce">TTA-based Codesign Environment (TCE)</a>
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</div>
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|
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<div class="doc_text">
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<p>
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<a href="http://tce.cs.tut.fi/">TCE</a> is a toolset for designing
|
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application-specific processors (ASP) based on the Transport triggered
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architecture (TTA). The toolset provides a complete co-design flow from C/C++
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|
programs down to synthesizable VHDL and parallel program binaries. Processor
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|
customization points include the register files, function units, supported
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|
operations, and the interconnection network.</p>
|
|
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|
<p>TCE uses llvm-gcc/Clang and LLVM for C/C++ language support, target
|
|
independent optimizations and also for parts of code generation. It generates
|
|
new LLVM-based code generators "on the fly" for the designed TTA processors and
|
|
loads them in to the compiler backend as runtime libraries to avoid per-target
|
|
recompilation of larger parts of the compiler chain.</p>
|
|
|
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</div>
|
|
|
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<!--=========================================================================-->
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<div class="doc_subsection">
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<a name="Horizon">Horizon Bytecode Compiler</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
<p>
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<a href="http://www.quokforge.org/projects/horizon">Horizon</a> is a bytecode
|
|
language and compiler written on top of LLVM, intended for producing
|
|
single-address-space managed code operating systems that
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run faster than the equivalent multiple-address-space C systems.
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|
More in-depth blurb is available on the <a
|
|
href="http://www.quokforge.org/projects/horizon/wiki/Wiki">wiki</a>.</p>
|
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|
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</div>
|
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<!--=========================================================================-->
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<div class="doc_subsection">
|
|
<a name="clamav">Clam AntiVirus</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
<p>
|
|
<a href="http://www.clamav.net">Clam AntiVirus</a> is an open source (GPL)
|
|
anti-virus toolkit for UNIX, designed especially for e-mail scanning on mail
|
|
gateways. Since version 0.96 it has <a
|
|
href="http://vrt-sourcefire.blogspot.com/2010/09/introduction-to-clamavs-low-level.html">bytecode
|
|
signatures</a> that allow writing detections for complex malware. It
|
|
uses LLVM's JIT to speed up the execution of bytecode on
|
|
X86, X86-64, PPC32/64, falling back to its own interpreter otherwise.
|
|
The git version was updated to work with LLVM 2.8.
|
|
</p>
|
|
|
|
<p>The <a
|
|
href="http://git.clamav.net/gitweb?p=clamav-bytecode-compiler.git;a=blob_plain;f=docs/user/clambc-user.pdf">
|
|
ClamAV bytecode compiler</a> uses Clang and LLVM to compile a C-like
|
|
language, insert runtime checks, and generate ClamAV bytecode.</p>
|
|
|
|
</div>
|
|
|
|
<!--=========================================================================-->
|
|
<div class="doc_subsection">
|
|
<a name="pure">Pure</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
<p>
|
|
<a href="http://pure-lang.googlecode.com/">Pure</a>
|
|
is an algebraic/functional
|
|
programming language based on term rewriting. Programs are collections
|
|
of equations which are used to evaluate expressions in a symbolic
|
|
fashion. Pure offers dynamic typing, eager and lazy evaluation, lexical
|
|
closures, a hygienic macro system (also based on term rewriting),
|
|
built-in list and matrix support (including list and matrix
|
|
comprehensions) and an easy-to-use C interface. The interpreter uses
|
|
LLVM as a backend to JIT-compile Pure programs to fast native code.</p>
|
|
|
|
<p>Pure versions 0.44 and later have been tested and are known to work with
|
|
LLVM 2.8 (and continue to work with older LLVM releases >= 2.5).</p>
|
|
|
|
</div>
|
|
|
|
<!--=========================================================================-->
|
|
<div class="doc_subsection">
|
|
<a name="GHC">Glasgow Haskell Compiler (GHC)</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
<p>
|
|
<a href="http://www.haskell.org/ghc/">GHC</a> is an open source,
|
|
state-of-the-art programming suite for
|
|
Haskell, a standard lazy functional programming language. It includes
|
|
an optimizing static compiler generating good code for a variety of
|
|
platforms, together with an interactive system for convenient, quick
|
|
development.</p>
|
|
|
|
<p>In addition to the existing C and native code generators, GHC 7.0 now
|
|
supports an <a
|
|
href="http://hackage.haskell.org/trac/ghc/wiki/Commentary/Compiler/Backends/LLVM">LLVM
|
|
code generator</a>. GHC supports LLVM 2.7 and later.</p>
|
|
|
|
</div>
|
|
|
|
<!--=========================================================================-->
|
|
<div class="doc_subsection">
|
|
<a name="Clay">Clay Programming Language</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
<p>
|
|
<a href="http://tachyon.in/clay/">Clay</a> is a new systems programming
|
|
language that is specifically designed for generic programming. It makes
|
|
generic programming very concise thanks to whole program type propagation. It
|
|
uses LLVM as its backend.</p>
|
|
|
|
</div>
|
|
|
|
<!--=========================================================================-->
|
|
<div class="doc_subsection">
|
|
<a name="llvm-py">llvm-py Python Bindings for LLVM</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
<p>
|
|
<a href="http://www.mdevan.org/llvm-py/">llvm-py</a> has been updated to work
|
|
with LLVM 2.8. llvm-py provides Python bindings for LLVM, allowing you to write a
|
|
compiler backend or a VM in Python.</p>
|
|
|
|
</div>
|
|
|
|
|
|
<!--=========================================================================-->
|
|
<div class="doc_subsection">
|
|
<a name="FAUST">FAUST Real-Time Audio Signal Processing Language</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
<p>
|
|
<a href="http://faust.grame.fr">FAUST</a> is a compiled language for real-time
|
|
audio signal processing. The name FAUST stands for Functional AUdio STream. Its
|
|
programming model combines two approaches: functional programming and block
|
|
diagram composition. In addition with the C, C++, JAVA output formats, the
|
|
Faust compiler can now generate LLVM bitcode, and works with LLVM 2.7 and
|
|
2.8.</p>
|
|
|
|
</div>
|
|
|
|
<!--=========================================================================-->
|
|
<div class="doc_subsection">
|
|
<a name="jade">Jade Just-in-time Adaptive Decoder Engine</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
<p><a
|
|
href="http://sourceforge.net/apps/trac/orcc/wiki/JadeDocumentation">Jade</a>
|
|
(Just-in-time Adaptive Decoder Engine) is a generic video decoder engine using
|
|
LLVM for just-in-time compilation of video decoder configurations. Those
|
|
configurations are designed by MPEG Reconfigurable Video Coding (RVC) committee.
|
|
MPEG RVC standard is built on a stream-based dataflow representation of
|
|
decoders. It is composed of a standard library of coding tools written in
|
|
RVC-CAL language and a dataflow configuration — block diagram —
|
|
of a decoder.</p>
|
|
|
|
<p>Jade project is hosted as part of the <a href="http://orcc.sf.net">Open
|
|
RVC-CAL Compiler</a> and requires it to translate the RVC-CAL standard library
|
|
of video coding tools into an LLVM assembly code.</p>
|
|
|
|
</div>
|
|
|
|
<!--=========================================================================-->
|
|
<div class="doc_subsection">
|
|
<a name="neko_llvm_jit">LLVM JIT for Neko VM</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
<p><a href="http://github.com/vava/neko_llvm_jit">Neko LLVM JIT</a>
|
|
replaces the standard Neko JIT with an LLVM-based implementation. While not
|
|
fully complete, it is already providing a 1.5x speedup on 64-bit systems.
|
|
Neko LLVM JIT requires LLVM 2.8 or later.</p>
|
|
|
|
</div>
|
|
|
|
<!--=========================================================================-->
|
|
<div class="doc_subsection">
|
|
<a name="crack">Crack Scripting Language</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
<p>
|
|
<a href="http://code.google.com/p/crack-language/">Crack</a> aims to provide
|
|
the ease of development of a scripting language with the performance of a
|
|
compiled language. The language derives concepts from C++, Java and Python,
|
|
incorporating object-oriented programming, operator overloading and strong
|
|
typing. Crack 0.2 works with LLVM 2.7, and the forthcoming Crack 0.2.1 release
|
|
builds on LLVM 2.8.</p>
|
|
|
|
</div>
|
|
|
|
<!--=========================================================================-->
|
|
<div class="doc_subsection">
|
|
<a name="DresdenTM">Dresden TM Compiler (DTMC)</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
<p>
|
|
<a href="http://tm.inf.tu-dresden.de">DTMC</a> provides support for
|
|
Transactional Memory, which is an easy-to-use and efficient way to synchronize
|
|
accesses to shared memory. Transactions can contain normal C/C++ code (e.g.,
|
|
<code>__transaction { list.remove(x); x.refCount--; }</code>) and will be executed
|
|
virtually atomically and isolated from other transactions.</p>
|
|
|
|
</div>
|
|
|
|
<!--=========================================================================-->
|
|
<div class="doc_subsection">
|
|
<a name="Kai">Kai Programming Language</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
<p>
|
|
<a href="http://www.oriontransfer.co.nz/research/kai">Kai</a> (Japanese 会 for
|
|
meeting/gathering) is an experimental interpreter that provides a highly
|
|
extensible runtime environment and explicit control over the compilation
|
|
process. Programs are defined using nested symbolic expressions, which are all
|
|
parsed into first-class values with minimal intrinsic semantics. Kai can
|
|
generate optimised code at run-time (using LLVM) in order to exploit the nature
|
|
of the underlying hardware and to integrate with external software libraries.
|
|
It is a unique exploration into world of dynamic code compilation, and the
|
|
interaction between high level and low level semantics.</p>
|
|
|
|
</div>
|
|
|
|
<!--=========================================================================-->
|
|
<div class="doc_subsection">
|
|
<a name="OSL">OSL: Open Shading Language</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
<p>
|
|
<a href="http://code.google.com/p/openshadinglanguage/">OSL</a> is a shading
|
|
language designed for use in physically based renderers and in particular
|
|
production rendering. By using LLVM instead of the interpreter, it was able to
|
|
meet its performance goals (>= C-code) while retaining the benefits of
|
|
runtime specialization and a portable high-level language.
|
|
</p>
|
|
|
|
</div>
|
|
|
|
|
|
|
|
<!-- *********************************************************************** -->
|
|
<div class="doc_section">
|
|
<a name="whatsnew">What's New in LLVM 2.8?</a>
|
|
</div>
|
|
<!-- *********************************************************************** -->
|
|
|
|
<div class="doc_text">
|
|
|
|
<p>This release includes a huge number of bug fixes, performance tweaks and
|
|
minor improvements. Some of the major improvements and new features are listed
|
|
in this section.
|
|
</p>
|
|
|
|
</div>
|
|
|
|
<!--=========================================================================-->
|
|
<div class="doc_subsection">
|
|
<a name="majorfeatures">Major New Features</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<p>LLVM 2.8 includes several major new capabilities:</p>
|
|
|
|
<ul>
|
|
<li>As mentioned above, <a href="#libc++">libc++</a> and <a
|
|
href="#lldb">LLDB</a> are major new additions to the LLVM collective.</li>
|
|
<li>LLVM 2.8 now has pretty decent support for debugging optimized code. You
|
|
should be able to reliably get debug info for function arguments, assuming
|
|
that the value is actually available where you have stopped.</li>
|
|
<li>A new 'llvm-diff' tool is available that does a semantic diff of .ll
|
|
files.</li>
|
|
<li>The <a href="#mc">MC subproject</a> has made major progress in this release.
|
|
Direct .o file writing support for darwin/x86[-64] is now reliable and
|
|
support for other targets and object file formats are in progress.</li>
|
|
</ul>
|
|
|
|
</div>
|
|
|
|
<!--=========================================================================-->
|
|
<div class="doc_subsection">
|
|
<a name="coreimprovements">LLVM IR and Core Improvements</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
<p>LLVM IR has several new features for better support of new targets and that
|
|
expose new optimization opportunities:</p>
|
|
|
|
<ul>
|
|
<li>The <a href="LangRef.html#int_libc">memcpy, memmove, and memset</a>
|
|
intrinsics now take address space qualified pointers and a bit to indicate
|
|
whether the transfer is "<a href="LangRef.html#volatile">volatile</a>" or not.
|
|
</li>
|
|
<li>Per-instruction debug info metadata is much faster and uses less memory by
|
|
using the new DebugLoc class.</li>
|
|
<li>LLVM IR now has a more formalized concept of "<a
|
|
href="LangRef.html#trapvalues">trap values</a>", which allow the optimizer
|
|
to optimize more aggressively in the presence of undefined behavior, while
|
|
still producing predictable results.</li>
|
|
<li>LLVM IR now supports two new <a href="LangRef.html#linkage">linkage
|
|
types</a> (linker_private_weak and linker_private_weak_def_auto) which map
|
|
onto some obscure MachO concepts.</li>
|
|
</ul>
|
|
|
|
</div>
|
|
|
|
<!--=========================================================================-->
|
|
<div class="doc_subsection">
|
|
<a name="optimizer">Optimizer Improvements</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<p>In addition to a large array of minor performance tweaks and bug fixes, this
|
|
release includes a few major enhancements and additions to the optimizers:</p>
|
|
|
|
<ul>
|
|
<li>As mentioned above, the optimizer now has support for updating debug
|
|
information as it goes. A key aspect of this is the new <a
|
|
href="SourceLevelDebugging.html#format_common_value">llvm.dbg.value</a>
|
|
intrinsic. This intrinsic represents debug info for variables that are
|
|
promoted to SSA values (typically by mem2reg or the -scalarrepl passes).</li>
|
|
|
|
<li>The JumpThreading pass is now much more aggressive about implied value
|
|
relations, allowing it to thread conditions like "a == 4" when a is known to
|
|
be 13 in one of the predecessors of a block. It does this in conjunction
|
|
with the new LazyValueInfo analysis pass.</li>
|
|
<li>The new RegionInfo analysis pass identifies single-entry single-exit regions
|
|
in the CFG. You can play with it with the "opt -regions -analyze" or
|
|
"opt -view-regions" commands.</li>
|
|
<li>The loop optimizer has significantly improved strength reduction and analysis
|
|
capabilities. Notably it is able to build on the trap value and signed
|
|
integer overflow information to optimize <= and >= loops.</li>
|
|
<li>The CallGraphSCCPassManager now has some basic support for iterating within
|
|
an SCC when a optimizer devirtualizes a function call. This allows inlining
|
|
through indirect call sites that are devirtualized by store-load forwarding
|
|
and other optimizations.</li>
|
|
<li>The new <A href="Passes.html#loweratomic">-loweratomic</a> pass is available
|
|
to lower atomic instructions into their non-atomic form. This can be useful
|
|
to optimize generic code that expects to run in a single-threaded
|
|
environment.</li>
|
|
</ul>
|
|
|
|
<!--
|
|
<p>In addition to these features that are done in 2.8, there is preliminary
|
|
support in the release for Type Based Alias Analysis
|
|
Preliminary work on TBAA but not usable in 2.8.
|
|
New CorrelatedValuePropagation pass, not on by default in 2.8 yet.
|
|
-->
|
|
|
|
</div>
|
|
|
|
<!--=========================================================================-->
|
|
<div class="doc_subsection">
|
|
<a name="mc">MC Level Improvements</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
<p>
|
|
The LLVM Machine Code (aka MC) subsystem was created to solve a number
|
|
of problems in the realm of assembly, disassembly, object file format handling,
|
|
and a number of other related areas that CPU instruction-set level tools work
|
|
in.</p>
|
|
|
|
<p>The MC subproject has made great leaps in LLVM 2.8. For example, support for
|
|
directly writing .o files from LLC (and clang) now works reliably for
|
|
darwin/x86[-64] (including inline assembly support) and the integrated
|
|
assembler is turned on by default in Clang for these targets. This provides
|
|
improved compile times among other things.</p>
|
|
|
|
<ul>
|
|
<li>The entire compiler has converted over to using the MCStreamer assembler API
|
|
instead of writing out a .s file textually.</li>
|
|
<li>The "assembler parser" is far more mature than in 2.7, supporting a full
|
|
complement of directives, now supports assembler macros, etc.</li>
|
|
<li>The "assembler backend" has been completed, including support for relaxation
|
|
relocation processing and all the other things that an assembler does.</li>
|
|
<li>The MachO file format support is now fully functional and works.</li>
|
|
<li>The MC disassembler now fully supports ARM and Thumb. ARM assembler support
|
|
is still in early development though.</li>
|
|
<li>The X86 MC assembler now supports the X86 AES and AVX instruction set.</li>
|
|
<li>Work on ELF and COFF object files and ARM target support is well underway,
|
|
but isn't useful yet in LLVM 2.8. Please contact the llvmdev mailing list
|
|
if you're interested in this.</li>
|
|
</ul>
|
|
|
|
<p>For more information, please see the <a
|
|
href="http://blog.llvm.org/2010/04/intro-to-llvm-mc-project.html">Intro to the
|
|
LLVM MC Project Blog Post</a>.
|
|
</p>
|
|
|
|
</div>
|
|
|
|
|
|
<!--=========================================================================-->
|
|
<div class="doc_subsection">
|
|
<a name="codegen">Target Independent Code Generator Improvements</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<p>We have put a significant amount of work into the code generator
|
|
infrastructure, which allows us to implement more aggressive algorithms and make
|
|
it run faster:</p>
|
|
|
|
<ul>
|
|
<li>The clang/gcc -momit-leaf-frame-pointer argument is now supported.</li>
|
|
<li>The clang/gcc -ffunction-sections and -fdata-sections arguments are now
|
|
supported on ELF targets (like GCC).</li>
|
|
<li>The MachineCSE pass is now tuned and on by default. It eliminates common
|
|
subexpressions that are exposed when lowering to machine instructions.</li>
|
|
<li>The "local" register allocator was replaced by a new "fast" register
|
|
allocator. This new allocator (which is often used at -O0) is substantially
|
|
faster and produces better code than the old local register allocator.</li>
|
|
<li>A new LLC "-regalloc=default" option is available, which automatically
|
|
chooses a register allocator based on the -O optimization level.</li>
|
|
<li>The common code generator code was modified to promote illegal argument and
|
|
return value vectors to wider ones when possible instead of scalarizing
|
|
them. For example, <3 x float> will now pass in one SSE register
|
|
instead of 3 on X86. This generates substantially better code since the
|
|
rest of the code generator was already expecting this.</li>
|
|
<li>The code generator uses a new "COPY" machine instruction. This speeds up
|
|
the code generator and eliminates the need for targets to implement the
|
|
isMoveInstr hook. Also, the copyRegToReg hook was renamed to copyPhysReg
|
|
and simplified.</li>
|
|
<li>The code generator now has a "LocalStackSlotPass", which optimizes stack
|
|
slot access for targets (like ARM) that have limited stack displacement
|
|
addressing.</li>
|
|
<li>A new "PeepholeOptimizer" is available, which eliminates sign and zero
|
|
extends, and optimizes away compare instructions when the condition result
|
|
is available from a previous instruction.</li>
|
|
<li>Atomic operations now get legalized into simpler atomic operations if not
|
|
natively supported, easing the implementation burden on targets.</li>
|
|
<li>We have added two new bottom-up pre-allocation register pressure aware schedulers:
|
|
<ol>
|
|
<li>The hybrid scheduler schedules aggressively to minimize schedule length when registers are available and avoid overscheduling in high pressure situations.</li>
|
|
<li>The instruction-level-parallelism scheduler schedules for maximum ILP when registers are available and avoid overscheduling in high pressure situations.</li>
|
|
</ol></li>
|
|
<li>The tblgen type inference algorithm was rewritten to be more consistent and
|
|
diagnose more target bugs. If you have an out-of-tree backend, you may
|
|
find that it finds bugs in your target description. This support also
|
|
allows limited support for writing patterns for instructions that return
|
|
multiple results (e.g. a virtual register and a flag result). The
|
|
'parallel' modifier in tblgen was removed, you should use the new support
|
|
for multiple results instead.</li>
|
|
<li>A new (experimental) "-rendermf" pass is available which renders a
|
|
MachineFunction into HTML, showing live ranges and other useful
|
|
details.</li>
|
|
<li>The new SubRegIndex tablegen class allows subregisters to be indexed
|
|
symbolically instead of numerically. If your target uses subregisters you
|
|
will need to adapt to use SubRegIndex when you upgrade to 2.8.</li>
|
|
<!-- SplitKit -->
|
|
|
|
<li>The -fast-isel instruction selection path (used at -O0 on X86) was rewritten
|
|
to work bottom-up on basic blocks instead of top down. This makes it
|
|
slightly faster (because the MachineDCE pass is not needed any longer) and
|
|
allows it to generate better code in some cases.</li>
|
|
|
|
</ul>
|
|
</div>
|
|
|
|
<!--=========================================================================-->
|
|
<div class="doc_subsection">
|
|
<a name="x86">X86-32 and X86-64 Target Improvements</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
<p>New features and major changes in the X86 target include:
|
|
</p>
|
|
|
|
<ul>
|
|
<li>The X86 backend now supports holding X87 floating point stack values
|
|
in registers across basic blocks, dramatically improving performance of code
|
|
that uses long double, and when targeting CPUs that don't support SSE.</li>
|
|
|
|
<li>The X86 backend now uses a SSEDomainFix pass to optimize SSE operations. On
|
|
Nehalem ("Core i7") and newer CPUs there is a 2 cycle latency penalty on
|
|
using a register in a different domain than where it was defined. This pass
|
|
optimizes away these stalls.</li>
|
|
|
|
<li>The X86 backend now promotes 16-bit integer operations to 32-bits when
|
|
possible. This avoids 0x66 prefixes, which are slow on some
|
|
microarchitectures and bloat the code on all of them.</li>
|
|
|
|
<li>The X86 backend now supports the Microsoft "thiscall" calling convention,
|
|
and a <a href="LangRef.html#callingconv">calling convention</a> to support
|
|
<a href="#GHC">ghc</a>.</li>
|
|
|
|
<li>The X86 backend supports a new "llvm.x86.int" intrinsic, which maps onto
|
|
the X86 "int $42" and "int3" instructions.</li>
|
|
|
|
<li>At the IR level, the <2 x float> datatype is now promoted and passed
|
|
around as a <4 x float> instead of being passed and returned as an MMX
|
|
vector. If you have a frontend that uses this, please pass and return a
|
|
<2 x i32> instead (using bitcasts).</li>
|
|
|
|
<li>When printing .s files in verbose assembly mode (the default for clang -S),
|
|
the X86 backend now decodes X86 shuffle instructions and prints human
|
|
readable comments after the most inscrutable of them, e.g.:
|
|
|
|
<pre>
|
|
insertps $113, %xmm3, %xmm0 <i># xmm0 = zero,xmm0[1,2],xmm3[1]</i>
|
|
unpcklps %xmm1, %xmm0 <i># xmm0 = xmm0[0],xmm1[0],xmm0[1],xmm1[1]</i>
|
|
pshufd $1, %xmm1, %xmm1 <i># xmm1 = xmm1[1,0,0,0]</i>
|
|
</pre>
|
|
</li>
|
|
|
|
</ul>
|
|
|
|
</div>
|
|
|
|
<!--=========================================================================-->
|
|
<div class="doc_subsection">
|
|
<a name="ARM">ARM Target Improvements</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
<p>New features of the ARM target include:
|
|
</p>
|
|
|
|
<ul>
|
|
<li>The ARM backend now optimizes tail calls into jumps.</li>
|
|
<li>Scheduling is improved through the new list-hybrid scheduler as well
|
|
as through better modeling of structural hazards.</li>
|
|
<li><a href="LangRef.html#int_fp16">Half float</a> instructions are now
|
|
supported.</li>
|
|
<li>NEON support has been improved to model instructions which operate onto
|
|
multiple consecutive registers more aggressively. This avoids lots of
|
|
extraneous register copies.</li>
|
|
<li>The ARM backend now uses a new "ARMGlobalMerge" pass, which merges several
|
|
global variables into one, saving extra address computation (all the global
|
|
variables can be accessed via same base address) and potentially reducing
|
|
register pressure.</li>
|
|
|
|
<li>The ARM backend has received many minor improvements and tweaks which lead
|
|
to substantially better performance in a wide range of different scenarios.
|
|
</li>
|
|
|
|
<li>The ARM NEON intrinsics have been substantially reworked to reduce
|
|
redundancy and improve code generation. Some of the major changes are:
|
|
<ol>
|
|
<li>
|
|
All of the NEON load and store intrinsics (llvm.arm.neon.vld* and
|
|
llvm.arm.neon.vst*) take an extra parameter to specify the alignment in bytes
|
|
of the memory being accessed.
|
|
</li>
|
|
<li>
|
|
The llvm.arm.neon.vaba intrinsic (vector absolute difference and
|
|
accumulate) has been removed. This operation is now represented using
|
|
the llvm.arm.neon.vabd intrinsic (vector absolute difference) followed by a
|
|
vector add.
|
|
</li>
|
|
<li>
|
|
The llvm.arm.neon.vabdl and llvm.arm.neon.vabal intrinsics (lengthening
|
|
vector absolute difference with and without accumulation) have been removed.
|
|
They are represented using the llvm.arm.neon.vabd intrinsic (vector absolute
|
|
difference) followed by a vector zero-extend operation, and for vabal,
|
|
a vector add.
|
|
</li>
|
|
<li>
|
|
The llvm.arm.neon.vmovn intrinsic has been removed. Calls of this intrinsic
|
|
are now replaced by vector truncate operations.
|
|
</li>
|
|
<li>
|
|
The llvm.arm.neon.vmovls and llvm.arm.neon.vmovlu intrinsics have been
|
|
removed. They are now represented as vector sign-extend (vmovls) and
|
|
zero-extend (vmovlu) operations.
|
|
</li>
|
|
<li>
|
|
The llvm.arm.neon.vaddl*, llvm.arm.neon.vaddw*, llvm.arm.neon.vsubl*, and
|
|
llvm.arm.neon.vsubw* intrinsics (lengthening vector add and subtract) have
|
|
been removed. They are replaced by vector add and vector subtract operations
|
|
where one (vaddw, vsubw) or both (vaddl, vsubl) of the operands are either
|
|
sign-extended or zero-extended.
|
|
</li>
|
|
<li>
|
|
The llvm.arm.neon.vmulls, llvm.arm.neon.vmullu, llvm.arm.neon.vmlal*, and
|
|
llvm.arm.neon.vmlsl* intrinsics (lengthening vector multiply with and without
|
|
accumulation and subtraction) have been removed. These operations are now
|
|
represented as vector multiplications where the operands are either
|
|
sign-extended or zero-extended, followed by a vector add for vmlal or a
|
|
vector subtract for vmlsl. Note that the polynomial vector multiply
|
|
intrinsic, llvm.arm.neon.vmullp, remains unchanged.
|
|
</li>
|
|
</ol>
|
|
</li>
|
|
|
|
</ul>
|
|
</div>
|
|
|
|
|
|
<!--=========================================================================-->
|
|
<div class="doc_subsection">
|
|
<a name="changes">Major Changes and Removed Features</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<p>If you're already an LLVM user or developer with out-of-tree changes based
|
|
on LLVM 2.7, this section lists some "gotchas" that you may run into upgrading
|
|
from the previous release.</p>
|
|
|
|
<ul>
|
|
<li>The build configuration machinery changed the output directory names. It
|
|
wasn't clear to many people that a "Release-Asserts" build was a release build
|
|
without asserts. To make this more clear, "Release" does not include
|
|
assertions and "Release+Asserts" does (likewise, "Debug" and
|
|
"Debug+Asserts").</li>
|
|
<li>The MSIL Backend was removed, it was unsupported and broken.</li>
|
|
<li>The ABCD, SSI, and SCCVN passes were removed. These were not fully
|
|
functional and their behavior has been or will be subsumed by the
|
|
LazyValueInfo pass.</li>
|
|
<li>The LLVM IR 'Union' feature was removed. While this is a desirable feature
|
|
for LLVM IR to support, the existing implementation was half baked and
|
|
barely useful. We'd really like anyone interested to resurrect the work and
|
|
finish it for a future release.</li>
|
|
<li>If you're used to reading .ll files, you'll probably notice that .ll file
|
|
dumps don't produce #uses comments anymore. To get them, run a .bc file
|
|
through "llvm-dis --show-annotations".</li>
|
|
<li>Target triples are now stored in a normalized form, and all inputs from
|
|
humans are expected to be normalized by Triple::normalize before being
|
|
stored in a module triple or passed to another library.</li>
|
|
</ul>
|
|
|
|
|
|
|
|
<p>In addition, many APIs have changed in this release. Some of the major LLVM
|
|
API changes are:</p>
|
|
<ul>
|
|
<li>LLVM 2.8 changes the internal order of operands in <a
|
|
href="http://llvm.org/doxygen/classllvm_1_1InvokeInst.html"><tt>InvokeInst</tt></a>
|
|
and <a href="http://llvm.org/doxygen/classllvm_1_1CallInst.html"><tt>CallInst</tt></a>.
|
|
To be portable across releases, please use the <tt>CallSite</tt> class and the
|
|
high-level accessors, such as <tt>getCalledValue</tt> and
|
|
<tt>setUnwindDest</tt>.
|
|
</li>
|
|
<li>
|
|
You can no longer pass use_iterators directly to cast<> (and similar),
|
|
because these routines tend to perform costly dereference operations more
|
|
than once. You have to dereference the iterators yourself and pass them in.
|
|
</li>
|
|
<li>
|
|
llvm.memcpy.*, llvm.memset.*, llvm.memmove.* intrinsics take an extra
|
|
parameter now ("i1 isVolatile"), totaling 5 parameters, and the pointer
|
|
operands are now address-space qualified.
|
|
If you were creating these intrinsic calls and prototypes yourself (as opposed
|
|
to using Intrinsic::getDeclaration), you can use
|
|
UpgradeIntrinsicFunction/UpgradeIntrinsicCall to be portable across releases.
|
|
</li>
|
|
<li>
|
|
SetCurrentDebugLocation takes a DebugLoc now instead of a MDNode.
|
|
Change your code to use
|
|
SetCurrentDebugLocation(DebugLoc::getFromDILocation(...)).
|
|
</li>
|
|
<li>
|
|
The <tt>RegisterPass</tt> and <tt>RegisterAnalysisGroup</tt> templates are
|
|
considered deprecated, but continue to function in LLVM 2.8. Clients are
|
|
strongly advised to use the upcoming <tt>INITIALIZE_PASS()</tt> and
|
|
<tt>INITIALIZE_AG_PASS()</tt> macros instead.
|
|
</li>
|
|
<li>
|
|
The constructor for the Triple class no longer tries to understand odd triple
|
|
specifications. Frontends should ensure that they only pass valid triples to
|
|
LLVM. The Triple::normalize utility method has been added to help front-ends
|
|
deal with funky triples.
|
|
</li>
|
|
<li>
|
|
The signature of the <tt>GCMetadataPrinter::finishAssembly</tt> virtual
|
|
function changed: the <tt>raw_ostream</tt> and <tt>MCAsmInfo</tt> arguments
|
|
were dropped. GC plugins which compute stack maps must be updated to avoid
|
|
having the old definition overload the new signature.
|
|
</li>
|
|
<li>
|
|
The signature of <tt>MemoryBuffer::getMemBuffer</tt> changed. Unfortunately
|
|
calls intended for the old version still compile, but will not work correctly,
|
|
leading to a confusing error about an invalid header in the bitcode.
|
|
</li>
|
|
|
|
<li>
|
|
Some APIs were renamed:
|
|
<ul>
|
|
<li>llvm_report_error -> report_fatal_error</li>
|
|
<li>llvm_install_error_handler -> install_fatal_error_handler</li>
|
|
<li>llvm::DwarfExceptionHandling -> llvm::JITExceptionHandling</li>
|
|
<li>VISIBILITY_HIDDEN -> LLVM_LIBRARY_VISIBILITY</li>
|
|
</ul>
|
|
</li>
|
|
|
|
<li>
|
|
Some public headers were renamed:
|
|
<ul>
|
|
<li><tt>llvm/Assembly/AsmAnnotationWriter.h</tt> was renamed
|
|
to <tt>llvm/Assembly/AssemblyAnnotationWriter.h</tt>
|
|
</li>
|
|
</ul>
|
|
</ul>
|
|
|
|
</div>
|
|
|
|
<!--=========================================================================-->
|
|
<div class="doc_subsection">
|
|
<a name="devtree_changes">Development Infrastructure Changes</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<p>This section lists changes to the LLVM development infrastructure. This
|
|
mostly impacts users who actively work on LLVM or follow development on
|
|
mainline, but may also impact users who leverage the LLVM build infrastructure
|
|
or are interested in LLVM qualification.</p>
|
|
|
|
<ul>
|
|
<li>The default for <tt>make check</tt> is now to use
|
|
the <a href="http://llvm.org/cmds/lit.html">lit</a> testing tool, which is
|
|
part of LLVM itself. You can use <tt>lit</tt> directly as well, or use
|
|
the <tt>llvm-lit</tt> tool which is created as part of a Makefile or CMake
|
|
build (and knows how to find the appropriate tools). See the <tt>lit</tt>
|
|
documentation and the <a href="http://blog.llvm.org/2009/12/lit-it.html">blog
|
|
post</a>, and <a href="http://llvm.org/bugs/show_bug.cgi?id=5217">PR5217</a>
|
|
for more information.</li>
|
|
|
|
<li>The LLVM <tt>test-suite</tt> infrastructure has a new "simple" test format
|
|
(<tt>make TEST=simple</tt>). The new format is intended to require only a
|
|
compiler and not a full set of LLVM tools. This makes it useful for testing
|
|
released compilers, for running the test suite with other compilers (for
|
|
performance comparisons), and makes sure that we are testing the compiler as
|
|
users would see it. The new format is also designed to work using reference
|
|
outputs instead of comparison to a baseline compiler, which makes it run much
|
|
faster and makes it less system dependent.</li>
|
|
|
|
<li>Significant progress has been made on a new interface to running the
|
|
LLVM <tt>test-suite</tt> (aka the LLVM "nightly tests") using
|
|
the <a href="http://llvm.org/docs/lnt">LNT</a> infrastructure. The LNT
|
|
interface to the <tt>test-suite</tt> brings significantly improved reporting
|
|
capabilities for monitoring the correctness and generated code quality
|
|
produced by LLVM over time.</li>
|
|
</ul>
|
|
</div>
|
|
|
|
<!-- *********************************************************************** -->
|
|
<div class="doc_section">
|
|
<a name="knownproblems">Known Problems</a>
|
|
</div>
|
|
<!-- *********************************************************************** -->
|
|
|
|
<div class="doc_text">
|
|
|
|
<p>This section contains significant known problems with the LLVM system,
|
|
listed by component. If you run into a problem, please check the <a
|
|
href="http://llvm.org/bugs/">LLVM bug database</a> and submit a bug if
|
|
there isn't already one.</p>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<div class="doc_subsection">
|
|
<a name="experimental">Experimental features included with this release</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<p>The following components of this LLVM release are either untested, known to
|
|
be broken or unreliable, or are in early development. These components should
|
|
not be relied on, and bugs should not be filed against them, but they may be
|
|
useful to some people. In particular, if you would like to work on one of these
|
|
components, please contact us on the <a
|
|
href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVMdev list</a>.</p>
|
|
|
|
<ul>
|
|
<li>The Alpha, Blackfin, CellSPU, MicroBlaze, MSP430, MIPS, SystemZ
|
|
and XCore backends are experimental.</li>
|
|
<li><tt>llc</tt> "<tt>-filetype=obj</tt>" is experimental on all targets
|
|
other than darwin-i386 and darwin-x86_64.</li>
|
|
</ul>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<div class="doc_subsection">
|
|
<a name="x86-be">Known problems with the X86 back-end</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<ul>
|
|
<li>The X86 backend does not yet support
|
|
all <a href="http://llvm.org/PR879">inline assembly that uses the X86
|
|
floating point stack</a>. It supports the 'f' and 't' constraints, but not
|
|
'u'.</li>
|
|
<li>Win64 code generation wasn't widely tested. Everything should work, but we
|
|
expect small issues to happen. Also, llvm-gcc cannot build the mingw64
|
|
runtime currently due to lack of support for the 'u' inline assembly
|
|
constraint and for X87 floating point inline assembly.</li>
|
|
<li>The X86-64 backend does not yet support the LLVM IR instruction
|
|
<tt>va_arg</tt>. Currently, front-ends support variadic
|
|
argument constructs on X86-64 by lowering them manually.</li>
|
|
</ul>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<div class="doc_subsection">
|
|
<a name="ppc-be">Known problems with the PowerPC back-end</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<ul>
|
|
<li>The Linux PPC32/ABI support needs testing for the interpreter and static
|
|
compilation, and lacks support for debug information.</li>
|
|
</ul>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<div class="doc_subsection">
|
|
<a name="arm-be">Known problems with the ARM back-end</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<ul>
|
|
<li>Thumb mode works only on ARMv6 or higher processors. On sub-ARMv6
|
|
processors, thumb programs can crash or produce wrong
|
|
results (<a href="http://llvm.org/PR1388">PR1388</a>).</li>
|
|
<li>Compilation for ARM Linux OABI (old ABI) is supported but not fully tested.
|
|
</li>
|
|
</ul>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<div class="doc_subsection">
|
|
<a name="sparc-be">Known problems with the SPARC back-end</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<ul>
|
|
<li>The SPARC backend only supports the 32-bit SPARC ABI (-m32); it does not
|
|
support the 64-bit SPARC ABI (-m64).</li>
|
|
</ul>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<div class="doc_subsection">
|
|
<a name="mips-be">Known problems with the MIPS back-end</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<ul>
|
|
<li>64-bit MIPS targets are not supported yet.</li>
|
|
</ul>
|
|
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<div class="doc_subsection">
|
|
<a name="alpha-be">Known problems with the Alpha back-end</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<ul>
|
|
|
|
<li>On 21164s, some rare FP arithmetic sequences which may trap do not have the
|
|
appropriate nops inserted to ensure restartability.</li>
|
|
|
|
</ul>
|
|
</div>
|
|
|
|
<!-- ======================================================================= -->
|
|
<div class="doc_subsection">
|
|
<a name="c-be">Known problems with the C back-end</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<p>The C backend has numerous problems and is not being actively maintained.
|
|
Depending on it for anything serious is not advised.</p>
|
|
|
|
<ul>
|
|
<li><a href="http://llvm.org/PR802">The C backend has only basic support for
|
|
inline assembly code</a>.</li>
|
|
<li><a href="http://llvm.org/PR1658">The C backend violates the ABI of common
|
|
C++ programs</a>, preventing intermixing between C++ compiled by the CBE and
|
|
C++ code compiled with <tt>llc</tt> or native compilers.</li>
|
|
<li>The C backend does not support all exception handling constructs.</li>
|
|
<li>The C backend does not support arbitrary precision integers.</li>
|
|
</ul>
|
|
|
|
</div>
|
|
|
|
|
|
<!-- ======================================================================= -->
|
|
<div class="doc_subsection">
|
|
<a name="llvm-gcc">Known problems with the llvm-gcc front-end</a>
|
|
</div>
|
|
|
|
<div class="doc_text">
|
|
|
|
<p>llvm-gcc is generally very stable for the C family of languages. The only
|
|
major language feature of GCC not supported by llvm-gcc is the
|
|
<tt>__builtin_apply</tt> family of builtins. However, some extensions
|
|
are only supported on some targets. For example, trampolines are only
|
|
supported on some targets (these are used when you take the address of a
|
|
nested function).</p>
|
|
|
|
<p>Fortran support generally works, but there are still several unresolved bugs
|
|
in <a href="http://llvm.org/bugs/">Bugzilla</a>. Please see the
|
|
tools/gfortran component for details. Note that llvm-gcc is missing major
|
|
Fortran performance work in the frontend and library that went into GCC after
|
|
4.2. If you are interested in Fortran, we recommend that you consider using
|
|
<a href="#dragonegg">dragonegg</a> instead.</p>
|
|
|
|
<p>The llvm-gcc 4.2 Ada compiler has basic functionality, but is no longer being
|
|
actively maintained. If you are interested in Ada, we recommend that you
|
|
consider using <a href="#dragonegg">dragonegg</a> instead.</p>
|
|
</div>
|
|
|
|
<!-- *********************************************************************** -->
|
|
<div class="doc_section">
|
|
<a name="additionalinfo">Additional Information</a>
|
|
</div>
|
|
<!-- *********************************************************************** -->
|
|
|
|
<div class="doc_text">
|
|
|
|
<p>A wide variety of additional information is available on the <a
|
|
href="http://llvm.org">LLVM web page</a>, in particular in the <a
|
|
href="http://llvm.org/docs/">documentation</a> section. The web page also
|
|
contains versions of the API documentation which is up-to-date with the
|
|
Subversion version of the source code.
|
|
You can access versions of these documents specific to this release by going
|
|
into the "<tt>llvm/doc/</tt>" directory in the LLVM tree.</p>
|
|
|
|
<p>If you have any questions or comments about LLVM, please feel free to contact
|
|
us via the <a href="http://llvm.org/docs/#maillist"> mailing
|
|
lists</a>.</p>
|
|
|
|
</div>
|
|
|
|
<!-- *********************************************************************** -->
|
|
|
|
<hr>
|
|
<address>
|
|
<a href="http://jigsaw.w3.org/css-validator/check/referer"><img
|
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src="http://jigsaw.w3.org/css-validator/images/vcss-blue" alt="Valid CSS"></a>
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<a href="http://validator.w3.org/check/referer"><img
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src="http://www.w3.org/Icons/valid-html401-blue" alt="Valid HTML 4.01"></a>
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|
|
<a href="http://llvm.org/">LLVM Compiler Infrastructure</a><br>
|
|
Last modified: $Date$
|
|
</address>
|
|
|
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</body>
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</html>
|